Imperial Valley Geothermal Energy

Ayana Wilson
November 30, 2010

Fig. 1: Illustration of a binary cycle
power plant. (Courtesy of
EERE,
U.S. Department of energy.)

Located along the volcanically and seismically active
region that spans up the pacific coasts of Australian and Asia down from
the northern tips of North America to the southernmost parts of South
America known as the Pacific Rim, California is home to 25 known
geothermal energy resource areas, one of which is the much discussed
Imperial Valley. Of the six known geothermal resource areas (KGRAs) in
the Imperial Valley, four have significant amounts of usable energy: The
Salton Sea, the Heber, East Mesa and the Brawley KGRA. The geothermal
reservoirs associated with these particular KGRAs use a binary cycle to
extract the heat instead of the dry-steam or vapor procedure used at The
Geysers in northern California because the geothermal fluids in the
valley are particularly scathing. [1]

Geothermal Energy Basics

Geothermal energy is the heat from the decay of
naturally radioactive materials (e.g. uranium and potassium) that is
transported through water conduction to the Earth's surface;
approximately 42 million megawatts of heat continuously flows by
conduction from the Earth's inner core outward, making geothermal energy
a completely renewable and sustainable energy resource. [2] To access
this natural thermal energy, industrialists drill wells miles into the
earth where hot reservoirs heated by magma or molten rock reach
temperatures of up to 700 degrees Fahrenheit. To get the heat energy
from the water at these depths in the Imperial Valley, a binary cycle is
used that pushes two fluids - geothermal fluid and a working fluid with
a boiling point much lower than that of water, such as isobutene -
through a heat exchanger. The heat energy from the geothermal fluid
evaporates the working fluid, and the resulting vapor pushes turbines to
generate electricity. Binary cycles are closed-loop systems, so the
working fluid is condensed and used for future cycles and no waste is
produced.

Water Wars

The $300 million geothermal energy business is not an
immediately ostensible threat to the $1.2 billion agricultural industry
that gives the Imperial Valley its economic livelihood. However, an
estimated 16,000 MW potential of renewable energy, comprised of solar,
wind, geothermal and biomass, lies in the valley alone, so the
agricultural center that is the Imperial Valley could soon give way to
the renewable energy movement. [3] This shift is already underway, as
companies like San Diego Gas & Electric, which has spent the past seven
years and about $100 million in the planning of a high voltage line,
called the Sunrise Powerlink, that would total 117 miles and run through
the heart of the alley, begin to buy government owned land. [4] In fact,
there are currently 16 geothermal plants throughout the valley, ten of
which are owned by CalEnergy, and the number will probably rise. [5]
According to U.S. Interior Secretary Dirk Kempthorne, 90% of U.S.
geothermal resources lie below federally owned land much of which could
be leased to businesses soon for geothermal energy production. [6] The
U.S. Department of the Interior's Bureau of Land Management (BLM) and
the USDA Forest Service (FS), which issued a report in July 2009 that
presented a survey of the geothermal potential of government owned lands
across 12 Western states, is encouraging these leases. [7] Still,
transforming the Imperial Valley into a hub for renewable energy
generation will be difficult not only because agricultural workers will
resist, but also and fundamentally because to function, geothermal
plants built in the region will need water from the very same resource
that provides irrigation for the crops: the Colorado river. [5] Water
from the Colorado River is regulated by the Law of the River established
in 1922; according to this law, 97% of the water that reaches the
Imperial Valley is for farmers, leaving only 96,000 ML for residents and
businesses, a third of which has been directed toward the geothermal
industry. [5] Water in all western states is lacking, and scientists
predict that in the case of the Colorado River, water supply will
diminish in the coming years due to climate change. Clearly then, the
drive toward geothermal, industrial excellence in the Imperial Valley
could very well dry up before even getting off the ground.